Experiments will examine the capacity of ascites fluid collected from 10 day old peritoneal tumors to interfere with the expression by macrophages of non-specific and specifically acquired immunity to the bacteria, Listeria monocytogenes. This will be determined by infusing ascites fluid into the peritoneal cavities of normal and Listeria-immune mice and then following the growth of an intraperitoneal challenge infection. Studies will also determine if the expression of concomitant anti-tumor immunity can be suppressed by injecting the secondary tumor cell challenge suspended in ascites fluid. In vitro studies will be conducted to test the affects of ascites fluid on the bactericidal and tumoricidal activities of macrophages. Experiments will also determine if the impairment of microbicidal activity of macrophages from ascites tumors can be reversed in vitro. Studies will investigate the ability of these macrophages to destroy bacteria after 3, 24, 48 and 72 hours in culture. Macrophages isolated from ascites tumors will also be exposed to endotoxin or lymphokines and then tested for bactericidal and tumoricidal activity. Pharmacologic triggering of macrophage activity will also be attempted with phorbol myristate acetate. In addition, macrophages from ascites tumors will be screened for the production and release of plasminogen activator by measuring the amount of 125I liberated from labelled fibrinogen. Studies will also determine if some of the macrophages which accumulate in ascites tumors have the capacity to proliferate in vitro.